Heat sink compositions are commonly used in industry where excess thermal energy is generated during any type of plant or industrial operation. For example, heat storage and heat retention are key aspects of many kiln designs and the designs of other types of high temperature processes where the retention of heat is critical to the cost performance of the industrial installation.
Heat storage bodies are generally composed of a number of materials including fired clays, sillimanite, mullite, magnesite and other types of mixed metal or metal oxides. These materials vary with respect to their physical properties including their heat storage capacities, their specific heat, thermal conductivity and their density.
In British Patent 1,262,475, a 100% Fe.sub.2 O.sub.3 heat storage composition is described for use in electric heating elements. This type of storage core is used to increase efficiency by storing radiant energy. Similarly, in Swiss Patent 453,626, a heat sink is described in which Fe.sub.3 O.sub.4 is used. This patent shows the oxidation from Fe.sub.3 O.sub.4 to Fe.sub.2 O.sub.4 is slow enough that a formulation based on Fe.sub.3 O.sub.4 is stable at the temperature ranges taught therein.
In U.S. Pat. No. 4,320,022 a dry granular magnetic fraction of asbestos tailings is used to form bricks and other types of heat storage cores. These compositions are made of magnesium oxide, silicon oxide and iron oxide with a special ratio between the magnesium and silica.
In U.S. Pat. No. 4,397,962 a heat or energy storage composition is described in which the element consists of 50-90% magnesium oxide and 5-50% iron oxide and a chemical binder. This is made into small particles and then used to form bricks or other types of shaped forms.
The above teachings all refer to either 100% iron oxide compositions or compositions having 50% or less of iron oxide or asbestos tailings for the manufacture of heat sink materials for recovery or retention of heat in electrical or other types of applications. Asbestos is undesirable for health reasons.